Fair Value Assets and Liabilities measured on nonrecurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carried at fair value	$ 2,090	$ 6,399
Loans Receivable, Fair Value Disclosure	6,441,458	5,580,780
Servicing Asset at Fair Value, Amount	5,800	1,200
Other Assets, Fair Value Disclosure	6,426,869	5,570,136
Other Repossessed Assets	4,200	4,000
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	2,090	6,399
Servicing Asset at Fair Value, Amount	5,797	1,169
Other Assets, Fair Value Disclosure	3,033	3,674
Other Repossessed Assets	3,599	3,464
Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	217	705
Nonrecurring basis | Construction Real Estate Remaining Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure		1,635
Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	1,873	4,059
Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	738	650
Nonrecurring basis | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	2,295	2,295
Nonrecurring basis | Construction Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure		729
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Repossessed Assets	0
Level 1 | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis | Construction Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	12,499	4,245
Level 2 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset at Fair Value, Amount	5,797	1,169
Other Assets, Fair Value Disclosure	0	0
Level 2 | Nonrecurring basis | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Repossessed Assets	0
Level 2 | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 2 | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 2 | Nonrecurring basis | Construction Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carried at fair value	2,090	6,399
Loans Receivable, Fair Value Disclosure	6,428,959	5,576,535
Other Assets, Fair Value Disclosure	6,426,869	5,570,136
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	2,090	6,399
Other Assets, Fair Value Disclosure	3,033	3,674
Other Repossessed Assets	3,599	3,464
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	217	705
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Construction Real Estate Remaining Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure		1,635
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	1,873	4,059
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	738	650
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	$ 2,295	2,295
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Construction Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure		$ 729